My bet here is that Simon's "death curse" looked like a major explosion followed by collapse of his fortress, and there was no checking for his body without moving hundreds of tons of rubble.

I could also entirely believe Simon rigging his fortress to blow, with the intent of then disappearing, and the Council taking it for granted it was a death curse.  If you look at the scenes in laFortier's room in TC, the Council's very best people are stretched to their limits to get really rather little information out of a crime scene in an environment over which they have complete control; even if they are going to risk sending their best investigators into a war zone, I don't believe they'd be able to get anywhere near so much information out of the remains of Archangel.

EXACTLY! I couldn't have elaborated better myself! Those are big things for me, in the Simon is Cowl argument. I don't think it possible that the Council would or could afford to spend time or wizards they need on the front lines and/or elsewhere in the War, looking at something which obviously seemed to be Simon using his Death Curse at Archangel and making sure that Simon and others were dead. From the ruins/rubble and everything, everything seemed to give indication of so, so why spend the time/effort that they DID NOT HAVE in confirming it?

They were already frantic, after all. Dealing with a huge war and an obvious traitor in their midst, though they didn't know where to look for the traitor.

oh you're such a fangirl

But I have to admit, it would be pretty funny (but then again, I like RDJ in his role of Iron Man becuase he's so arrogant and stuff). I'd actually watch it

I am, I admit it!

(RDJ is literally perfect for the role of Tony Stark.) Yeah, I think it'd be fun to watch. xD

Oh I can see it now. 

Jarvis:  Sir, we are experiencing widespread system failure. 

Stark:  What? Why? 

Jarvis:  It appears to be emanating from the glowing gentleman shooting fire from his hands.  May I suggest you should land before-

Stark:  Oh, Crap. 
*sputter sputter, POP*

AAAAAHHHhhhhhhhhhhh

LOL! Totally! XD I can easily see that happening.

I don't see how it would be easy for a White Council trained wizard to live 250-300 years while amassing such skill and power without his peers (similarly old and powerful wizards) knowing about him.

Oh no, it's definitely possible; Aizen in Bleach held back how powerful he truly was for hundreds of years without being detected. I would think it most definitely be possible, especially if they are noted to be powerful, like Simon. Aizen was so powerful, he was able to trick some of the most powerful characters with illusions that they couldn't even detect them until he pointed them out. I think Simon just chose to leave when it was time/the opportunity presented itself and/or something came up, like a plan beginning/starting to come to fruition.

mmm. I was thinking more, composed largely of young teenagers, who fairly visibly span the entire range of maturiity and social cluefulness that one might expect of young teenagers; myself, I am going to be 40 this year, and the things I get out of it and like talking about with relation to it are probably not the same as the things many of those young teenagers are connecting to.  (Intelligent time-travel that's not afraid of being complex for the win. Also, metafiction for a better tomorrow.  But drawing trolls... not so much me.) It also strikes me as a very weird outlier in terms of how I think about fanfic generally because of the extent to which Hussie embraces and trolls his fandom.

That's a good point.
I'm not quite a teenager anymore either, though I do understand a few things as well. I couldn't draw any Trolls even if I wanted to--I suck at drawing unless looking at a picture of something.

We don't, but would Larisa still be acting like an apprentice decades later?

No, probably not but I think she'd be willing to go along with him, especially if it meant keeping an eye on her Mentor who may or may not have something wrong with him (i.e Infected).

In fact it may also be out of Obligation. Here's a thought I wonder if many have put forth: perhaps she was brought back by Simon.

Maybe her death was kind of a catalyst & he lost it at Archangel (Nemesis may or may not be a part of it.) He either releases a DC at Archangel, fakes one or someone else threw it. After that he flees in the ensuing chaos, takes up the name Cowl, reviving Larisa.

After that, he somehow comes across the Fomor, makes a deal with them (maybe they had a hand in heping bring Larisa back) -which would explain the voice Harry heard in DB- & gets word (somehow) that Kemmler's book is in Chicago.

He is curious to see Harry's skills..

Recall that Harry needed Micheals help. Cowl would probably have needed Kumori's help.

And Simon had a female apprentice...

I usually just use WordPad.

(Though don't start me on Homestuck fandom.)

Yes, the Homestuck fandom is quite complex lol.

I thought you were into HS! Your icon 1mm3d14t3ly m4d3 m3 th1nk of T3r3z1 lol.

I myself got into it a few months ago on a friends recommendation. Are you caught up with it?